Variable track wheel

ABSTRACT

A variable track wheel ( 1 ) comprises a rim ( 2 ) suitable for receiving a tire, and a disc ( 3 ) through which said wheel ( 1 ) is mountable on a hub ( 37 ), said disc ( 3 ) being removably secured by fastenings ( 6 ) to a connecting member ( 4 ) provided in said rim ( 2 ), said connecting member ( 4 ) projecting towards a rotation axis (X) of said wheel ( 1 ), said wheel further comprising a plurality of spacers ( 15 ) interposed between an annular perimeter zone ( 36 ) of said disc ( 3 ) and said connecting member ( 4 ) of said rim ( 2 ), said disc ( 3 ) and said rim ( 2 ) being mountable in a plurality of reciprocal axial positions and in a plurality of reciprocal orientations to obtain a variation in the track of said wheel ( 1 ), said wheel ( 1 ) further comprising at least one centring device ( 8; 9 ) for mutual positioning of said disc ( 3 ) and of said rim ( 2 ), said centring device ( 8; 9 ) comprising a hole ( 10; 10   a;    10   b ) and a pin ( 11 ), said hole ( 10; 10   a;    10   b ) or said pin ( 11 ) being provided in said connecting member ( 4 ) or in said disc ( 3 ), said centring device ( 8; 9 ) further comprising a coupling element ( 21 ) so conformed as to cooperate with said hole ( 10; 10   a;    10   b ) and with said pin ( 11 ) for reciprocally coupling said pin ( 11 ) and said hole ( 10; 10   a;    10   b ).

This application claims priority to International Patent CooperationTreaty Application Serial No. PCT/IB2012/057315, filed on Dec. 10, 2012,which claims priority to European Patent Application No. 11194646.3filed on Dec. 20, 2011, which is incorporated herein in its entirety bythis reference.

BACKGROUND OF THE INVENTION

The invention relates to a variable track wheel of the type comprising arim and a disc mounted together in a removable manner.

Variable track wheels comprising a rim are known, on which the tyre ismounted, having a cylindrical base on the internal circumferal surfaceof which there is provided a connecting member that projects radiallytowards the rotation axis of the wheel. A disc is removably secured tothe connecting member, the wheel being fitted to a hub by means of thedisc. The connecting member comprises a circumferally continuous singleannular element or a plurality of circumferally equidistant lobes.

The disc is secured to the connecting member by fastenings, such asfixing bolts, passing through connecting holes provided in both disc andconnecting member. As the disc has a concave face and a correspondingconvex fact, by varying the axial mounting position between the rim anddisc, or by rotating the disc around the vertical diameter thereof, thedistance varies between the median plane of the rim and the plane of thehub against which the disc is mounted, this causing a pair of wheels onthe same axle to be brought nearer or moved further away. Such wheelsare, for example, used as wheels of agricultural machines, such astractors, in which, to comply with different agricultural applications,the rim and the disc must be able to be assembled according toalternative axial positions or orientations.

One drawback of variable track wheels of known type is that as they arewheels of relatively large dimensions, it is rather difficult toassemble the disc and the rim in such a manner that the respectiverotation axes are effectively coaxial. In fact, gravity and the playbetween the fixing bolts and the connecting holes provided on both discand connecting member, to ensure assembly thereof, cause the axis of thedisc, once mounted, not to be aligned on the axis of the rim. This axialmisalignment between rim and disc has a negative effect on the strokeand performance features of the vehicle on which the wheel is mounted.In particular, the misalignment causes vibrations that are transmittedto the vehicle, with the risk of causing the driver problems of comfortor even problems of safety due to instability of the vehicle.

This is particularly relevant to vehicles that are arranged fortravelling at relatively high speeds, for example even at 50 kilometersan hour.

Variable track wheels are known in which the misalignment of the axes ofthe disc and of the rim has been considered.

EP0808250 discloses a variable track wheel in which the disc is providedwith additional holes that during mounting are aligned on at least twoindicators or holes provided on the rim and reciprocally coupled bycentring plugs that can be removed once the fixing bolts have beentightened.

EP0911183 discloses a variable track wheel wherein the disc is providedwith a pair of diametrically opposite centring pins, arranged forcoupling with a plurality of pairs of corresponding diametricallyopposite holes obtained on the connecting member. The centring systemsof known type are not designed for repeating centring during mounting ofthe disc and of the rim after first mounting.

In fact, during removal of the centring pins or during subsequentinserting of the pins into the corresponding holes, the walls of theholes into which the centring pins have to be inserted for centring canbecome damaged, this causing possible play that reduces the precision ofthe subsequent mounting.

Still another drawback of known systems is that in the event ofreplacement of only the rim or only the disc with a new rim or a newdisc, the new rim or the new disc has to be provided with holes or pinshaving dimensions that are compatible with those found on the piece withwhich they have to be coupled. This means that a large number of spareparts have to be kept in store so that one disc model can be mounted ona plurality of models of rim and vice versa the same centring system canbe maintained.

Alternatively, to mount, for example, a new disc on an old rim, it isnecessary to work on the old rim or on the new disc, for example, tomatch the dimensions of the holes with those of the pins, thisincreasing significantly the time and cost of replacement. Lastly, thecentring systems of known type are not effective on all the types ofvariable track wheel, in particular on wheels comprising spacers betweenthe disc and connecting member.

One object of the invention is to improve the centring systems of knowntype to limit the misalignment of the axes of the disc and of the rim ofa wheel. A further object is to obtain a variable track wheel in whichthe disc and the rim can be replaced individually with spare parts,without it being necessary to perform mechanical machinings to adapt thecentring system of the spare part with that of the disc and/or of therim that has not been replaced.

Still another object is to provide a centring system that can be appliedto a variable track wheel comprising spacers between the disc andconnecting member. Another object is to obtain a variable track wheel inwhich the mounting position between disc and rim ensures a set balanceof the wheel.

A still further object is to produce a variable track wheel, in whichthe mounting position between disc and rim corresponding to a setbalance of the wheel can be refound with a certain precision at eachreassembly of the disc of the rim following the first mounting duringmanufacture.

According to the invention, a variable track wheel is providedcomprising a rim that is suitable for receiving a tyre, and a discthrough which said wheel is mountable on a hub, said disc beingremovably secured by fastenings to a connecting member provided in saidrim, said connecting member projecting towards a rotation axis of saidwheel, said wheel further comprising a plurality of spacers interposedbetween an annular perimeter zone of said disc and said connectingmember of said rim, said disc and said rim being mountable in aplurality of reciprocal axial positions and in a plurality of reciprocalorientations to obtain a variation in the track of said wheel, saidwheel further comprising at least one centring device for mutualpositioning of said disc and of said rim, said centring devicecomprising a hole and a pin, said hole or said pin being provided insaid connecting member or in said disc, characterised in that saidcentring device further comprises a coupling element shaped in such amanner as to cooperate with said hole and with said pin for mutuallycoupling said pin and said hole.

Owing to the coupling element, the diameter of the hole/pin provided onthe connecting member can also be substantially different from thediameter of the pin/hole provided on the disc, inasmuch as it is thecoupling element that adapts the dimensions of the hole to those of thepin.

In one embodiment, the wheel comprises two centring devices, each ofwhich is provided with a corresponding coupling element.

In a further embodiment, the two centring devices are diametricallyopposite and are dimensionally different from one another, i.e. the pin,the hole and the coupling element of the first centring device havedimensions—in particular the diameter—other than those of the respectivepin, hole and coupling element of the second centring device.

This enables the mounting position of the rim and of the disc to befound unequivocally, whatever the mutual axial position or orientationof the rim and disc, and enables a set balance of the wheel to beobtained.

As the wheel comprises spacers that are interposed between saidconnecting member and said disc and retained between said connectingmember and said disc by the fastenings, in particular by bolts, thecoupling element, in addition to coupling the pin with the hole,compensates the distance imposed by the spacers between the disc and theconnecting member.

BRIEF DESCRIPTION OF THE FIGURES

The invention can be better comprised and implemented with reference tothe attached drawings, which illustrate one embodiment thereof by way ofnon-limiting example, in which:

FIG. 1 is a front view of a variable track wheel;

FIG. 2 is an enlarged cross section taken along the plane II-II in FIG.1;

FIG. 3 is an enlarged cross section taken along the plane III-III inFIG. 1;

FIG. 4 is an enlarged cross section taken along the plane IV-IV in FIG.1;

FIG. 5 is an enlarged view of the section in FIG. 3;

FIG. 6 shows fragmentary and shrunk cross sections of the wheel in FIG.1 corresponding to axial positions that are different from one anotherof the wheel and of a hub.

FIGS. 1 and 2 show a variable track wheel 1, comprising a rim 2 that issuitable for receiving a tyre, which is not shown, and a disc 3 throughwhich the wheel 1 is mountable on a hub, which is also shown.

The rim 2 comprises a connecting member 4, that projects from aninternal circumferal surface 5 of the rim 2 to a rotation axis X of thewheel 1.

The connecting member 4 comprises a circumferally continuous singularannular element, which is fixed to the internal circumferal surface 5for example by welding, in particular angular welding, indicated by W inFIGS. 1 and 2.

In one alternative embodiment that is not shown, instead of acircumferally continuous singular annular element, the connecting member4 can comprise a plurality of circumferally equidistant lobes.

The connecting member 4 is substantially flat, i.e. extends parallel toa central diametral plane of the rim 2—and thus of the wheel 1, of lineM in FIG. 2, at a preset distance K from the latter.

The disc 3 comprises a flat central region 30 in which a central opening31 is provided that is arranged for receiving a portion of the hub. Inthe flat central region 30 a plurality of peripheral openings 32 arealso provided that are angularly equidistant from one another and arearranged around the central circular opening 31, to mount the disc 3,and thus the wheel 1, on the hub, by means of removable connecting meanssuch as, for example, bolts. The disc 3 further comprises a shapedregion 33, for example of conical shape, which can include a firstconical portion 34 and a second conical portion 35, wherein the firstconical portion 34 has an angle at the vertex of the cone correspondingthereto that is greater than the angle at the vertex of the conecorresponding to the second conical portion 35. The disc 3 furthercomprises a flange region 36 of annular and substantially flat shape,arranged for facing the connecting member 4.

Between the disc 3 and the connecting member 4 spacers 15 areinterposed. The disc 3 is removably secured to the connecting member 4by fastenings, in particular bolts 6, each bolt 6 comprising a screw 6 aand a nut 6 b. One or more washers 7 can be associated with the bolt 6in the known manner. Each bolt 6 is received in a passage 12 provided inthe connecting member 4 and in a fixing hole 13 provided in the disc 3,in particular in the flange region 36. Each bolt 6 is then received in athrough hole 14 of the respective spacer 15, which is interposed betweenthe connecting member 4 and the disc 3 at each passage 12 and eachfixing hole 13.

In the embodiment shown, on the connecting member 4 six passages 12 areprovided, and respectively on the disc 3 six fixing holes 13 areprovided. The passages 12 and the fixing holes 13 are angularlyequidistant. In the embodiment shown, six spacers 15 are thereforeprovided.

The spacers 15 have a set thickness S, by means of which it is possibleto obtain a plurality of tracks that are different from one anotheraccording to the position and orientation of the disc 3 with respect tothe rim 2 and of the rim 2 with respect to the hub.

The wheel 1 comprises one centring device for mutual positioning of thedisc 3 and of the rim 2.

In particular, the wheel 1 comprises of pair of centring devices 8, 9for mutual positioning of the disc 3 of the rim 2.

The pair of centring devices 8, 9 comprises a first centring device 8and a second centring device 9, which are in particular diametricallyopposite one another.

Each centring device 8, 9 is arranged in a respectively intermediatezone between two consecutive bolts 6.

The first centring device 8 and a second centring device 9 are inparticular arranged substantially at the same distance from the rotationaxis (X).

Subsequently, the common elements of the first centring device 8 and ofthe second centring device 9 are indicated by the same referencenumbers.

With reference to FIG. 5, each centring device 8, 9 comprises a hole 10and a pin 11, the hole 10 being provided in the connecting member 4 andthe pin 11 being mounted on the disc 3.

The pin 11 is mounted with forced coupling or interference in an opening16 of the disc 3, in particular, the pin 11 comprises a central, forexample knurled, zone 17, intended for being in contact with walls ofthe opening 16, The pin 11 further comprises a first end 18 protrudingfrom the disc 3 to the connecting member 4. The pin 11 can furthercomprise a second end 19, opposite the first end 18, protruding from aface of the disc 3 opposite the face from which the first end 18protrudes. The first end 18 and the second end 19, which are bothcylindrical in shape, have diameters that are substantially the same asone another. Hereinafter, when reference is made to the dimensions, andin particular to the diameter, of the pin 11, the dimensions, and inparticular the diameter, of one of the protruding ends of the pin 11 ismeant, namely of the first end 18 or of the second end 19.

The fact that the first end 18 and the second end 19 protrude from facesof the disc 3 that are opposite one another enables the same pin 11 tobe used for centring between disc 3 and rim 2 also in the configurationin which the disc 3 is rotated by 180° with respect to the centraldiametral plane M of the rim 2, as will be disclosed below.

Each centring device 8, 9 further comprises a coupling element 21cooperating with the hole 10 and with the pin 11 for reciprocallycoupling the pin 11 and the hole 10. The coupling element 21 comprises abody provided with a first portion 23, for example of cylindrical shape.

The first portion 23 is provided with a cavity 25, arranged forreceiving in a shapingly coupled manner the first end 18, or the secondend 19, of the pin 11. The cavity 25 extends centrally to the firstportion 23.

The first portion 23 is interposed between the connecting member 4 andthe disc 3. The first portion 23 is provided with a first arrestingsurface 26 and with a second arresting surface 27 intended forcontacting respectively the connecting member 4 and the disc 3.

Further, the first portion 23 compensates the distance between the disc3 and the connecting member 4 set by the spacers 15. Thus the firstportion 23 has a longitudinal extent D that is substantially the same asthe thickness S of the spacer 15.

The body of the coupling element 21 further comprises a second portion24, which projects from the first portion 23 so as to form a stem. Inparticular, the stem 24 projects from the first arresting surface 26,centrally thereto.

The second portion or stem 24 is so conformed as to be received in ashapingly coupled manner in the hole 10 of the connecting member 4. Thestem 24 is housed in the hole 10 with free coupling.

The coupling element 21 enables the dimensions of the pin 11 to bedisconnected from those of the hole 10 and vice versa.

In fact, the difference in dimensions, in particular in diameter, thatmay be present between the pin 11 and the hole 10 is compensated by thecoupling element 21.

Thus the coupling element 21 enables only the disc or only the rim of avariable track wheel to be replaced without it being necessary toimplement mechanical machinings on the disc and/or on the rim to becoupled to maintain the centring device effective. In other words, thecoupling element acts as an adapter, which enables the pin to becompatible with the dimensions of the hole.

If, for example, in the case of replacement of the rim or of the disc,the pin on the disc has too small a diameter compared with the diameterof the hole on the connecting member, the centring device does notoperate, inasmuch as the excessive play between pin and hole does notpermit precise coupling and thus sufficiently precise alignment of theaxis of the rim and of the axis of the disc. In this case, the couplingelement 21 will be conformed as to ‘increase’ the reduced dimensions ofthe pin, such as to make the coupling between pin and hole of thecentring device more precise.

In the absence of the coupling element 21 that is specifically shapedfor adapting to the dimensions of the pin 11, it would be necessary toremove the pin 11 from the forced coupling with the opening 16, widenthis opening 16 and mount therein a new pin of larger dimensions thatare compatible with the hole 10; alternatively it would be necessary towiden the hole 10 on the connecting member 4 or provide a new hole 10.Such operations might not be easily performable on the place in whichthe disc or the rim is replaced, with the risk of damaging the disc orthe connecting member and making the centring device ineffective.Further, such operations could modify the weight of the disc and/or ofthe rim, thus causing the wheel to be no longer balanced.

Similarly, if, for example, in the event of replacement of the rim or ofthe disc, the pin on the disc has a diameter that is greater than thediameter of the hole on the connecting member, the centring device mightnot be reused. In this case, it is sufficient to provide a couplingelement that is specifically shaped to house the pin, for example thecavity 25 will have a diameter that is such as to house in a shapinglycoupled manner the pin 11 of greater dimensions, whereas the stem 24will have substantially the same dimensions as the hole 10.

The coupling element 21 will thus be shaped in such a manner as to adaptto the dimensions of the hole 10 and to the dimensions of the pin 11 andin this manner adapt that hole 10 to that pin 11.

In other words, instead of machining mechanically the spare parts or theparts on which the latter are mounted, it is possible to provide acertain range of coupling elements that differ from one another throughthe dimensions of the opening and of the stem to reuse the couplingdevice in the event of replacement. Such coupling elements enable theparts of the centring device to be adapted that are arrangedrespectively on the disc and on the rim. Owing to the coupling element,it is possible to choose a centring device in which the hole hasdifferent dimensions from the pin.

In particular, the two centring devices 8, 9 can differ from one anotherby the respective dimensions of the hole or of the pin.

In the embodiment illustrated in FIGS. 3 and 4, the first centringdevice 8 (FIG. 3) comprises a hole 10 a of diameter L1 and the secondcentring device 9 (FIG. 4) comprises a hole tab of diameter L2, whereinL1 and L2 are different from one another. The first centring device 8thus comprises a first coupling element 21 a provided with a stem 24 aof a diameter that is such as to be housed in the hole 10 a with freecoupling. In other words, the diameter of the stem 24 a is substantiallythe same as the diameter L1 or the hole 10 a, less the couplingtolerance. Similarly, the second centring device 9 comprises a secondcoupling element 21 b having a stem 24 b of a diameter that is such asto be housed in the hole 10 b with free coupling. In other words, thediameter of the stem 24 b is substantially the same as the diameter L2of the hole 10 b, less the coupling tolerance. In this embodiment, thepin of the first centring device 8 and the pin of the second centringdevice 9 are the same as one another and these pins are indicated by thesame reference number 11. Consequently, also the cavity 25 has the samedimensions on the two coupling elements 21 a and 21 b.

In one embodiment that is not shown, the hole 10 can be provided on thedisc 3 and the pin 11 on the connecting member 4. In this embodiment,the coupling element 21 is arranged rotated by 180° around a diametralplane of the rim with respect to the arrangement shown in FIG. 4 of thecoupling element 20, i.e. the stem 24 is to the right of the cavity 25,not to the left, as shown in FIG. 4, and both stem 24 and cavity 25 willextend from left to right, and not from right to left as in FIG. 4.

The centring devices 8, 9 are made during manufacture of the wheel 1.

The disc 3 and the rim 2 are arranged substantially concentrically in amask. Naturally, the manufacturing tolerances of the passage 12 on theconnecting member 4 of the fixing hole 13 on the disc 3, and of thethrough hole 14 on the spacer 15 are such as to enable the position ofthe disc 3 to be adjusted in relation to the rim 2 in such a manner asto be able to align together the passages 12, the fixing holes 13 andthe through hole 14 before the bolts 6 are tightened and thesubstantially concentric position of the disc 3 and rim 2 is fixed.

In the substantially concentric position of the disc 3 and of the rim 2,the holes 10, or 10 a and 10 b are made respectively on the connectingmember 4 and the openings 16, or 16 a and 16 b, on the disc 3.

Subsequently, the bolts 6 are loosened and the disc 3 and the rim 2 areagain moved away, such that the pins 11 can be mounted on the disc 3.The coupling element 21, or 21 a and 21 b, is associated with thecorresponding pin 11. By again repositioning the disc 3 and the rim 2 onthe mark in the substantially concentric position, the coupling element21, or 21 a and 21 b, is now inserted into the hole 10, or 10 a and 10b, and the first portion 23 is interposed between the disc 3 and the rim2. The bolts 6 are tightened and the mask is removed.

At this point the wheel 1 is ready for being subjected to balancing andmarking.

Marking the rim at the high—or positive value point of the firstharmonic of the wheel—is known, which first harmonic is defined as theassembly of the rim and of the disc—and marking the wheel at the low—ornegative—value point of the first harmonic of the wheel, By mounting thewheel on the rim in such a manner that the position of the high value ofthe wheel substantially coincides with the position of the low value ofthe wheel, compensation is obtained of the geometrical manufacturingerrors and of the distribution of the masses of the wheel and of thetyre, which are one of the causes of vibrations in the vehicle. In thismanner, lack of uniformity of the wheel-tyre assembly is minimised,increasing the comfort of the driver of agricultural vehicles that areintended to travel at 50 km/h.

In all the embodiments disclosed above, owing to the coupling element21, it is possible to find at each reassembly of the rim 2 and of thedisc 3 the alignment position of the respective axis, in which presetbalancing of the wheel 1 is obtained.

The coupling element 21, or 21 a and 21 b, enables centring of variabletrack wheels to be obtained, in which varying of the wheel track ispossible owing to the presence of spacers, such as the spacers 15 in theembodiments shown.

The disc 3 and the rim 2 can also be mounted according to positions thatare different from one another that are illustrated in FIG. 6. Withreference to FIG. 6, A-H indicate the different distances that areobtainable between the central diametral plane M of the wheel 1 and amounting plan N of the hub 37 against which the disc 3 is mounted whenthe axial mounting position between the rim 2 and disc 3 is varied, forexample by mounting the flange region to the left of the connectingmember rather than to the right and/or by rotating the disc 3 around thevertical diameter.

Varying the distance between the central diametral plane M and themounting plane N of the hub 37 moves a pair of wheels 1 of the vehiclenearer or further that are mounted on the same axle.

FIG. 6 illustrates how the position of the connecting element 21 varieswith the varying of the position between the disc 3 and rim 2.

The connecting element 21 ensures that the rim 2 and the disc 3 can bereassembled in the substantially concentric position even when the trackof the vehicle on which the wheel 1 is mounted is varied, in accordancewith one of the corresponding positions of the disc 3 and rim 2 shown inFIG. 6.

Further, the embodiment in which two centring devices 8 and 9 areprovided that are different from one another, ensures in an effectivemanner that the assembly of the rim 2 on the disc 3 occurs on the samesubstantially concentric position made during the wheel 1 manufacturingstep, without the risk that the coupling element 21 a can be coupledwith the hole 10 b, if diametrically opposite, or vice versa that thecoupling element 21 b can be coupled with the hole 10 a.

This significantly limits the possibility of an error in mounting therim 2 on the disc 3, in particular in the event of replacement of thetyre, in which the disc 3 remains mounted on the axis of the wheels ofthe vehicle and the rim 2 is remounted on the disc 3 that is alreadyprovided with the new tyre. It should be observed that the wheels ofagricultural vehicles such as tractors are rather bulky and positioningthe rim with respect to the disc directly on the vehicle can be ratherdifficult when in the field.

We claim:
 1. A variable track wheel comprising a rim suitable forreceiving a tire, and a disc through which said wheel is mountable on ahub, said disc being removably secured by fastenings to a connectingmember provided in said rim, said connecting member projecting towards arotation axis of said wheel, said wheel further comprising a pluralityof spacers interposed between an annular perimeter zone of said disc andsaid connecting member of said rim, said disc and said rim beingmountable in a plurality of reciprocal axial positions and in aplurality of reciprocal orientations to obtain a variation in the trackof said wheel, said wheel further comprising at least one centringdevice for mutual positioning of said disc and of said rim, saidcentring device comprising a hole and a pin, said hole or said pin beingprovided in said connecting member or in said disc, characterized inthat said centring device further comprises a coupling element conformedto cooperate with said hole and with said pin for reciprocally couplingsaid pin and said hole, wherein said coupling element comprises a firstportion wherein a cavity is obtained, arranged for receiving in ashaping coupled manner an end of said pin and said first portion isconformed to compensate the distance between said disc and saidconnecting member, said first portion being interposed between saidconnecting member and said disc, wherein said first portion is providedwith a first arresting surface and with a second arresting surfaceintended for contacting respectively said connecting member and saiddisc.
 2. The wheel according to claim 1, wherein said cavity extendscentrally to said first portion.
 3. The wheel according to claim 2,wherein said coupling element further comprises a second portion, thatprojects from said first portion so as to form a stem, said stem beingconformed to be received in a shapingly coupled manner in said hole. 4.The wheel according to claim 3, wherein said stem projects from asubstantially central portion of said first arresting surface.
 5. Thewheel according to claim 2, further comprising: a. a further centringdevice, substantially conformed as said centring device; b. a furtherpin; and c. a further coupling element, said centring device and saidfurther centring device being arranged at a distance that issubstantially equal distance from said rotation axis.
 6. The wheelaccording to claim 5, wherein said further centring device isdiametrically opposite said centring device.
 7. The wheel according toclaim 5, wherein said further centring device differs from said centringdevice by a diameter of said further hole and/or of said further pinand/or of said further coupling element, when compared with thecorresponding diameter of said hole and/or of said pin (11) and/or ofsaid coupling element.